Fixed timing cam actuated gas exchange valves for internal combustion engines are beginning to give way to structures that allow for some timing variation in either the opening or closing timing of either, or both of, an intake valve and an exhaust valve. These mechanisms include, but are not limited to, devices that can adjust the phase angle of a cam relative to the crank shaft, mechanisms with the ability to hold a valve open beyond its normal cam dictated closing timing, and possibly even camless actuators, such as an electro-hydraulic actuator, that enable complete control over valve opening and closing timing independent of crank shaft angle. Those skilled in the art have long recognized that the ability to vary valve timing can allow for performance improvements, reduced emissions, and oftentimes both.
Like any engine component, a variable valve mechanism can fail. Oftentimes an engine can be equipped with electronic fault detection algorithms in its electronic control module for monitoring various engine components for failure, including variable valve actuators. If a fault is detected, the operator is often notified via an indicator light or the like instructing them to seek servicing of the engine. It is known that fault detectors can sometimes issue a false positive. In such a case, a fault notification can cause an operator to have a variable valve actuator mistakenly replaced when it is actually working properly. Thus, a false positive in a fault detection algorithm can lead to unnecessary down time along with the substantial expense associated with replacing a good component. Apart from this problem, there are often difficulties in quickly confirming that a newly installed or replaced variable valve actuator is operating properly.
The present invention is directed to one or more of the problems set forth above.